There is considerable interest in modulating the efficacy of currently used antiproliferative agents to increase the rates and duration of antitumor effects associated with conventional antineoplastic agents.
Conventional antiproliferative agents used in the treatment of cancer are broadly grouped as (1) chemical compounds which affect the integrity of nucleic acid polymers by binding, alkylating, inducing strand breaks, intercalating between base pairs or affecting enzymes which maintain the integrity and function of DNA and RNA; (2) chemical agents that bind to proteins to inhibit enzymatic action (e.g., antimetabolites) or the function of structural proteins necessary for cellular integrity (e.g., antitubulin agents). Other, chemical compounds that have been identified to be useful in the treatment of some cancers include drugs which block steroid hormone action for the treatment of breast and prostate cancer, photochemically activated agents, radiation sensitizers, and protectors.
Of special interest to this invention are those compounds that directly affect the integrity of the genetic structure of the cancer cells. Nucleic acid polymers such as DNA and RNA are prime targets for anticancer drugs. Alkylating agents such as nitrogen mustards, nitrosoureas, aziridine containing compounds directly attack DNA. Metal coordination compounds such as cisplatin and carboplatin similarly directly attack the nucleic acid structure resulting in lesions that are difficult for the cells to repair which, in turn, can result in cell death. Other nucleic acid affecting compounds include anthracycline molecules such as doxorubicin, which intercalates between the nucleic acid base pairs of DNA polymers, bleomycin, which causes nucleic acid strand breaks, fraudulent nucleosides such as pyrimidine and purine nucleoside analogs, which are inappropriately incorporated into nucleic polymer structures and ultimately cause premature DNA chain termination. Certain enzymes that affect the integrity and functionality of the genome can also be inhibited in cancer cells by specific chemical agents and result in cancer cell death. These include enzymes that affect ribonucleotide reductase (e.g., hydroxyurea, gemcitabine), topoisomerase I (e.g., camptothecin) and topoisomerase II (e.g., etoposide).
One of the most broadly used of these DNA targeted anticancer drugs is cisplatin (cis-diamminedichloroplatinum II, CDDP). This compound is active against several human cancers including testicular, small-cell lung, bladder, cervical and head and neck cancer.
Although the clinical activity of currently approved antiproliferative agents against many forms of cancers can be shown, improvements in tumor response rates, duration of response and ultimately patient survival are still sought. The invention described herein demonstrates the novel use of the naphthalimides and analogs thereof, including amonafide, which can potentiate the antitumor effects of chemotherapeutic drugs, in particular, agents affecting the integrity of nucleic polymers such as DNA.